Method and device for indicating the direction of rotation of a three-phase system

ABSTRACT

A method and measuring device are provided for measuring the direction of rotation of a three-phase system. The measurement is carried out by measuring sensors. A coupling circuit is connected to each measuring sensor and transforms the voltage produced in the measuring sensor into rectangular pulses. The coupling circuit outputs are connected to a common logic device which determines the direction of rotation on the basis of the phase difference between the pulses.

This application is a 371 of PCT/FI93/00267, filed Jun. 22, 1993.

The object of the invention is a method and measuring device formeasuring the direction of rotation of a three-phase system, themeasurement being carried out by means of measuring sensors.

An electrical voltage with a varying direction is called alternatingvoltage. Periodic alternating voltage is a voltage, the variation ofwhich is repeated in similar form at certain intervals.

If a coil is rotated at constant angular speed in a homogenous magneticfield, a sinusoidal supply voltage is induced. A one-phase system isachieved when the coil is connected to a loading circuit. If coils areplaced on the surface of a rotor at random, and a separate loadingcircuit is connected to each coil, a multiphase system is achieved.

The multiphase system is symmetrical if all its supply voltages areequally high and if the phase angle difference between the supplyvoltages is equal; otherwise it is asymmetrical.

The most common symmetrical multiphase system is the three-phase system.Since the number of phases of the system is three, the angle differencebetween the phase coils of the generator is 120°. As the positivedirection of the supply voltages to be induced in phase coils we canselect the direction from the end of the phase to its beginning. Thephase sequence is then 1, 2, 3. If the rotor's direction of rotation ischanged, the phase sequence becomes negative: 1, 3, 2.

By connecting three circuits together, the conductors can be partlyshared by the different circuits. An electricity source for alternatingcurrent or an electrical apparatus to be connected to an electricalinstrument is connected by joining either the beginnings or ends of thephase coils into a star point; similarly, in serial connection, theelectrical apparatus is connected by joining the phase coils into aclosed ring by always connecting the end of a phase coil to thebeginning of the following phase coil.

At present, measuring the direction of rotation of a voltage in fieldconditions--when connecting electrical apparatus and installing newapparatus--is carried out galvanically on the live parts of athree-phase system, the measurement thus having to be done on bareconductor surfaces. The conductor insulation on the conductor surfacehas to be peeled off, and to the bare conductor surface is fastened aso-called alligator clamp or the like, which is connected to themeasuring device through a conductor.

The disadvantages of the above known method are that the manner ofmeasuring is not occupationally safe and carrying out the measurementalone in field conditions is difficult. In addition, the traditionalmeasuring device must be connected when de-energized, that is, thesupply of electricity must be disconnected for a moment.

The aim of the present invention is to eliminate the above-mentionedproblems and to achieve a new method and measuring device whichfacilitate measurements in field conditions, and which are at the sametime occupationally safe.

It is characteristic of the method relating to the invention that ameasuring sensor operating on the electrostatic principle is mountedadjacent to each three-phase system wire, that the alternating voltageproduced in the measuring sensors is transformed by means of anelectronic coupling circuit or the like into rectangular pulses, thatthe pulse sequences obtained from all measuring sensors are transmittedto a logic circuit or microprocessor circuit which determines thedirection of rotation on the basis of the phase difference between thepulses.

It is characteristic of the device relating to the invention that, aftereach measuring sensor a coupling circuit is connected, transforming thevoltage produced in the measuring sensor into rectangular pulses, andthat the coupling circuit outputs are connected to a common logic ormicroprocessor which determines the direction of rotation on the basisof the phase difference between the pulses.

By means of the invention a measuring device is achieved, with which thedirection of rotation can be measured on the conductor insulationsurface, without galvanic contact. When the device is used, theconductor insulation on the conductors leading to the electricalappliance does not have to be removed, which at the same timefacilitates and speeds up the measurement of the direction of rotation.Measurement can thus be carried out on a live wire, merely taking intoaccount the safety distances complying with safety regulations.

The invention is exemplified in the following with reference to theaccompanying drawings, in which

FIG. 1 shows an axonometric view of the measuring device relating to theinvention,

FIG. 2 shows a diagrammatic view of the operating principle of themeasuring device relating to the invention, and

FIG. 3 shows a diagrammatic view of the operating principle of thesecond measuring device embodiment relating to the invention.

FIG. 1 shows an axonometric view of the measuring device 10 formeasuring the direction of rotation of the voltage of a three-phasesystem. The measuring device 10 is intended for measuring the directionof rotation of a three-phase system electrostatically, by means ofmeasuring sensors 11. Due to the sensitivity of the device 10, themeasuring sensor 11 can measure the direction of rotation of the voltagein the wire even at a distance of 4 cm.

The logic of the measuring device 10 is built into the housing 16.Manual devices 12 acting as the insulators of the measuring sensors 11are connected through the front plate 19 of the housing 16 to themeasuring circuit by means of wires 15. The ends of the measuringsensors 11 are bent in order to render them more suitable for fittingaround the conductors or wires of the three-phase system. At the ends ofthe measuring sensors are fitted plugs 18. The manual devices 12incorporate fixed stops 17 fitted at their centre, with the purpose ofpreventing the hand holding the device from coming into contact with thelive wire being measured.

Inside the insulator casing of the manual devices 12 are installed someof the electronics required for measuring, including for example thetransistor 21 connected to the measuring sensor 11, a resistor 31 and atransistor 22, as shown in FIG. 2. After each measuring sensor 11 isthus connected a coupling circuit, 21 and 22, which transforms thevoltage produced in the measuring sensor 11 into rectangular pulses. Theoutputs of the coupling circuits 21 and 22 are connected to the logicbuilt into a common housing 16, the said logic indicating the directionof rotation on the basis of the phase difference between pulses.

The housing 16 contains the measuring logic of the actual measuringdevice 10 shown in FIG. 2. On the cover plate 20 are fixed leds 68, 69and 70, identifying the different phases by means of signal lamps. Theleds provided with red 65 and green 66 signal lamps indicate whether thedirection of voltage of a three-phase system being measured is corrector incorrect. The signal lamp 67 shows readiness for operation and, whenilluminated, indicates that the measuring logic is not ready foroperation. With the help of the signal lamp 67 it can be concludedwhether the voltage of the battery acting as the power source for themeasuring device is sufficient. The signal lamp 67 goes out when themeasuring device 10 indicates the direction of rotation. To the side 9of the housing 16 is attached the power switch K of the measuring device10. The measuring device 10 operates on both 110 V and 220 V voltages.

FIG. 2 shows a diagrammatic view of the operating principle of anembodiment of a measuring device relating to the invention. When themeasuring sensor 11 in the manual device 12 of the measuring device 10for measuring the static direction of rotation is brought into thevicinity of an alternating voltage conductor, the transistor 21 in themanual device 12 opens, thus producing a base voltage in the transistor22 over the resistor 31, and making the transistor 22 conductive. Thecurrent can then pass through the transistor 22 and the resistor 33 tothe negative pole 13, 14. The circuit generating the base voltage of theNPN transistor 21 consists of a resistor 98 and, alongside the resistor98, the capacitance of any point in the circuit to earth which is shownschematically and in broken line at 99 in FIG. 2.

When the sensor 11 of the manual device 12 is sufficiently close to thelive conductor, that is, when the sensor is in a sufficiently highalternating voltage field, the voltage over the resistor 98 and theearth capacitance 99 rises higher than 0.6 V. As a result of this thetransistor 21 becomes conductive, that is, opens. The transistor 21opens only during the positive phase of the mains voltage, in which casea 50 Hz rectangular wave can be measured over the resistor 33. Theserectangular waves are conducted from each phase of the measuring sensors11, through amplifiers 43, 44 and 45 to an R/S trigger element 50.

The directions of rotation to be measured are indicated in such a waythat the rectangular wave of each single phase in the three-phase systemis conducted to the J-input 52 and K-input 53 and timer input 51 of theR/S trigger element 50, which triggers the S-output 55 or R-output 56 ofthe R/S trigger element 50, energizing one of them, depending on whichone of the rectangular waves of the J-input 52 or K-input 53 is ahead ofthe other, that is, which phase voltage is ahead of the other at themoment of triggering, because the phase difference between the voltagesof the three-phase system is always 120°. Triggering takes place on thefalling edge of the pulse. After triggering the R/S trigger element 50remains in the same state until the state of the J-input 52 or K-input53 changes with respect to the moment of triggering.

By means of the above-described coupling arrangement, a direct voltageis produced in the R-output 56 or S-output 55 of the circuit formed bythe R/S trigger element 50. This direct voltage is conducted through theresistors 36 or 35 to the leds 65 or 66 indicating the direction ofrotation, and further through the transistor 23 to the negative pole 14.

By means of the transistor 33 and the AND gate 60, the leds 65 and 66are prevented from lighting up until all three sensors 11 of themeasuring device 10 have been connected to measure. Blocking is carriedout so that the pulses of the sensors 11 are brought to the input pins61, 62 and 63 of the AND gate, filtered through the circuit formed bythe resistors 37, 38 and 39, and capacitors 71, 72 and 73 and alsothrough the diodes 95, 96 and 97. Similarly, the positive operatingvoltage 57 is brought to the AND gate 60. After filtering, the voltagesat the input pins 61, 62 and 63 of the AND gate can be seen as directvoltages at the AND gate 60.

The output 64 of the AND gate 60 is energized once all the input pulseshave been connected and the positive operating voltage has been switchedon by means of switch K, which means that through two invertingamplifiers 47 and 48, and through resistor 34, the transistor 23receives base current and is energized, thus allowing the leds 65 and 66to light up. The inverting amplifier 49 and resistor 32 in the output 64of the AND gate 60, cause the led 67 indicating readiness for operationto light up, which, when illuminated, indicates that the measuring logicis not ready for operation. From the signal lamp led 67 it can at thesame time be deduced that the battery has sufficient voltage. The signallamp led 67 goes out when the measuring device 10 indicates thedirection of rotation. The amplifiers 89-94 control the signal lamp leds68, 69 and 70 which, when lighting up, indicate that the field receivedby the sensor 11 is of sufficient magnitude.

FIG. 3 shows a diagrammatic view of the operating principle of thesecond measuring device embodiment relating to the invention. Whereapplicable, the same reference numbers are used in the diagram of FIG. 3as in FIG. 1, by merely adding the number "1" in front of the referencenumber.

After the measuring sensor 111 operating on the same principle as thatshown in FIG. 2, a coupling circuit 121, 122 is connected, transformingthe voltage produced in the measuring sensor into rectangular pulses.The outputs 121, 122 of the coupling circuit are connected to a commonmicroprocessor built into a housing, the microprocessor determining thedirection of rotation on the basis of the phase difference between thepulses.

The housing corresponds to the housing shown in FIG. 1 and on its coverplate are fixed leds 168, 169 and 170 identifying different phases bymeans of signal lamps. The leds provided with red 165 and green 166signal lamps indicate whether the direction is correct or incorrect. Thesignal lamp 167 indicates the battery's readiness for operation. As inFIG. 1, to the side of the housing is attached the power switch K of themeasuring device 110. The measuring device 110 operates on both 110 Vand 220 V voltages. The measuring device can be used to establish thephases of two different systems having the same signs.

According to the operating principle of the measuring device shown inFIG. 3, the directions of rotation to be measured are indicated in sucha way that the rectangular wave of each single phase in the three-phasesystem is conducted to the input gates p5, p6, and p7 of themicroprocessor 150. The program in the processor 150 establishes theorder in which the rectangular pulses come to the gates p5, p6 and p7,and on the basis of this determines from the 120° phase differencebetween the pulses the direction of rotation of the system. The programalso controls the phase identification leds 168, 169 and 170, as guidedby the gates p10, p11, and p12 of the processor 150, with the help ofthe amplifier 200.

The device relating to FIG. 3 can be provided with a "self test"function which checks, whenever power is switched to the device fromswitch K1, that the input gates of the processor 150 have notshort-circuited for one reason or another. The testing is carried out sothat the program conducts voltage from the processor gate p9 to gate p6,after which the processor reads the states of all input gates p5, p6,and p7 and lights up the leds 168, 169 and 170 identifying the phase,and keeps them illuminated for about 2 seconds. If the inputs of thedevice are in order, only led 169 may light up.

The measuring device can be used to find out the equiangular phases oftwo different systems by switching voltage by switch K2 to the inputgate p8 which transfers the processor program to an area which checksfor cophasality. Cophasality can be established by means of the sensors112 and 112'. When the sensors are in the same phase, both leds 165 and166 indicating the direction of rotation are lit up by the program,through the amplifier 200.

It is obvious to one skilled in the art that the different embodimentsof the invention may vary within the scope of the claims presentedbelow. Thus, for example in measuring sensors connected to measuringdevices, micro circuits can be used instead of transistors.

I claim:
 1. A measuring device for measuring the direction of rotationof a three-phase system, comprising:a plurality of electrostaticmeasuring sensors; a coupling circuit connected to each measuring sensorfor transforming voltage induced in the measuring sensor to which it isconnected into rectangular pulses, each said coupling circuit having aninput connected to one of said electrosatic measuring sensors, and anoutput; a logic circuit, common to said coupling circuits, whichdetermines direction of rotation based upon the phase differencesbetween said pulses from each of said coupling circuits; and means forindicating the direction of rotation of the three-phase system; andwherein said logic circuit comprises a trigger element connecting saidindicating means to said outputs of said coupling circuits, and an ANDgate operatively connected to said indicating means and preventing saidindicating means from being activated until all of said sensors areconnected to said logic circuit.
 2. A device as recited in claim 1wherein said plurality of electrostatic measuring sensors comprisesthree sensors.
 3. A device as recited in claim 2 wherein each of saidelectrostatic measuring sensors comprises an electrically conductiveelement having a hook-shaped free end, and an insulating material casingmounted to said conductive element spaced from said hook-shaped freeend.
 4. A device as recited in claim 3 wherein each of said insulatingmaterial casings contains therein a said coupling circuit, resistor, andearth capacitance; and further comprising a fixed stop mounted to acenter portion of each of said insulating material casings.
 5. A deviceas recited in claim 3 further comprising a housing enclosing said commonlogic circuit, said housing connected to said electrostatic measuringsensors and coupling circuits by wires extending from said insulatingmaterial casings thereto.
 6. A device as recited in claim 1 wherein eachcoupling circuit comprises at least one transistor which becomesconductive in a positive or negative half-cycle of the voltage inducedin the electrostatic measuring sensor with which it is associated.
 7. Adevice as recited in claim 1 wherein said logic circuit includes amicroprocessor.
 8. A device as recited in claim 1 wherein saidindicating means comprises a plurality of LEDs connected to said logiccircuit for indicating the direction of rotation of the three-phasesystem; and wherein said logic circuit further comprises a transistoroperatively connected to said AND gate and said LEDs through a filteringcircuit, so that said LEDs are prevented from being energized until allof said sensors have been connected to said AND gate.
 9. A device asrecited in claim 8 further comprising a first signal lamp LED connectedto said logic circuit in such a way that it is not energized when one ofsaid direction of rotation LEDS is energized, and a plurality of othersignal lamp LEDs operatively connected to said sensors so thatenergization of each of said signal lamp LEDs indicates that the sensorassociated therewith is receiving a measurable induced voltage.
 10. Ameasuring device for measuring the direction of rotation of athree-phase system, comprising:means for measuring the direction ofrotation of a three-phase system having conductors with insulationthereon, without galvanic contact with the conductors, so that saidinsulation does not have to be removed, or with earth, said meanscomprising: a plurality of electrostatic measuring sensors; a couplingcircuit connected to each measuring sensor for transforming voltageinduced in the measuring sensor to which it is connected intorectangular pulses, each said coupling circuit having an input connectedto one of said electrostatic measuring sensors, and an output; a logiccommon to said coupling circuits which determines direction of rotationbased upon the phase differences between said pulses from each of saidcoupling circuits; and means for indicating the direction of rotation ofthe three-phase system; and wherein said logic circuit comprises atrigger element connecting said indicating means to said outputs of saidcoupling circuits, and an AND gate operatively connected to saidindicating means and preventing said indicating means from beingactivated until all of said sensors are connected to said logic circuit.11. A device as recited in claim 10 wherein each coupling circuitcomprises at least one transistor which becomes conductive in a positiveor negative half-cycle of the voltage induced in the electrostaticmeasuring sensor with which it is associated.
 12. A device as recited inclaim 10 wherein each of said electrostatic measuring sensors comprisesan insulating material casing, and wherein each of said insulatingmaterial casings contains therein a said coupling circuit, as well as aresistor, and earth capacitance coupled to one of said electrostaticmeasuring sensors for providing a base voltage to the coupling circuitassociated with that sensor; and further comprising a fixed stop mountedto a center portion of each of said insulating material casings.
 13. Amethod of measuring the direction of rotation of a three-phase systemhaving three conductive wires covered by electrical insulation, usingthree electrostatic measuring sensors, a plurality of LEDs indicatingthe direction of rotation of the three-phase system, and an AND gate;said method comprising the steps of:(a) bringing each electrostaticmeasuring sensor into close proximity to, but not galvanic contact with,one of the three conductive wires covered by electrical insulationduring rotation of the three-phase system, rotation of the three-phasesystem inducing alternating voltage pulses in each of the sensors; (b)transforming the alternating voltage pulses from each of the sensors instep (a) into distinct rectangular pulses; (c) calculating the directionof rotation of the three-phase system by evaluating the phasedifferences between the distinct rectangular pulses from step (b); (d)preventing energization of the LEDs until all three sensors have beenoperatively connected to the AND gate; and (e) energizing the LEDs toindicate the direction of rotation calculated in the practice of step(c).
 14. A method as recited in claim 13 wherein each of the sensorsincludes an electrically conductive element having a hook-shaped freeend, and an insulating material casing mounted to the conductive elementspaced from the hook-shaped free end; and wherein step (a) is practicedby manually holding and manipulating the insulating material casings tofit the hook-shaped free ends thereof around the wires of thethree-phase system.
 15. A method as recited in claim 13 wherein step (b)is practiced for each sensor by generating a base voltage in a firsttransistor, and transmitting an induced voltage from the sensor to asecond transistor to make the second transistor conductive.
 16. A methodas recited in claim 13 utilizing a microprocessor with gates, andwherein step (c) is practiced by establishing the order that rectangularpulses are received by the gates of the microprocessor.
 17. A method asrecited in claim 13 utilizing an R/S trigger element having a J-input,K-input, and timer input, and an S-output and R-output; and wherein step(c) is practiced by conducting each rectangular wave from each sensor tothe J, K, and timer inputs of the R/S trigger element, therebytriggering the S or R-outputs on the falling edge of a pulse energizingone of them, depending upon which one of the rectangular waves isreceived ahead of the other at the J or K-inputs at the moment oftriggering.
 18. A method as recited in claim 17 wherein step (c) isfurther practiced by maintaining the R/S trigger element in the samestate until the state of the J or K-input changes with respect to themoment of triggering.
 19. A method as recited in claim 17 furtherutilizing a resistor connected to LEDs indicating the direction ofrotation of the three-phase system, the LEDs in turn connected through atransistor to a negative pole; and wherein step (c) is further practicedby conducting a direct voltage produced in the R or S-outputs throughthe resistor to the LEDs, indicating the direction of rotation, and thenthrough the transistor to the negative pole.
 20. A device as recited inclaim 10 wherein said indicating means comprises a plurality of LEDsconnected to said logic circuit for indicating the direction of rotationof the three-phase system; and wherein said logic circuit furthercomprises a transistor operatively connected to said AND gate and saidLEDs through a filtering circuit, so that said LEDs are prevented frombeing energized until all of said sensors have been connected to saidAND gate.